Question

Could someone help me explain this? I have two snippets of code, one works as I expect, but the other does not.

This works

$a = array('a' => 1, 'b' => 2);
$b = array('c' => 3);
$c = $a + $b;
print_r($c);

// Output
Array
(
    [a] => 1
    [b] => 2
    [c] => 3
)

This does not

$a = array('a', 'b');
$b = array('c');
$c = $a + $b;
print_r($c);

// Output
Array
(
    [0] => a
    [1] => b
)

What is going on here?? Why doesn’t the second version also add the two arrays together? What have I misunderstood? What should I be doing instead? Or is it a bug in PHP?

Answer 1

This is documented and correct: https://www.php.net/manual/en/language.operators.array.php

The + operator appends elements of remaining keys from the right handed array to the left handed, whereas duplicated keys are NOT overwritten.

So I guess it’s not a bug in php and what is suppose happen. I hadn’t noticed this before either.